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<p>Due to their sustainable, versatile, and highly customizable properties, cellulose nanocrystals (CNCs) are regarded as highly promising alternatives to fossil-based materials. However, conventional production of these materials has attracted a lot of environmental and economic concerns, negatively impacting their usability. Subcritical water technology has provided a “greener” yet economic approach to produce these materials with competitive properties. Still, due to the low accessibility of cellulose to water and inhibited esterification reaction rates in the presence of water, the process suffers from low yields of unfunctionalized CNCs. This work employs common mechanical pretreatments (blade grinding, wet ball milling, and refining) to access their fibrillation efficiencies and influence on CNC yield from subcritical water treatment. The initial fibrillation from mechanical pretreatments before subcritical water extraction led to increased exposure and swelling of individual fibers, enhancing maximum solvent accessibility and efficient dissolution of undesirable amorphous regions to increase the overall yield (about 40%) of isolated nanocrystals. During extraction of these materials, the extraction water is catalyzed with an acid blend containing citric acid to produce low surface charge carboxylated CNCs (about 80–200&#xa0;mmol/kg cellulose). Dispersibility results reveal that the CNCs are colloidally stable in water and maintain this stability for at least 7&#xa0;days without any sonication. Thermogravimetric analyses also show that these small amounts of surface groups do not negatively affect the thermal stability of the isolated CNCs, having higher thermal stability than sulfated CNCs. The results from this study contribute significantly to improving subcritical water technology for the industrial isolation of high-yield cellulose nanocrystals without using harsh and toxic chemicals.</p> Graphical abstract <p></p>

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Improving yield and colloidal stability of cellulose nanocrystals isolated via assisted subcritical water hydrolysis: influence of mechanical pretreatments and esterifying agents on cellulose hydrolysis in subcritical water

  • 期刊论文

  • 发表日期：

    2025年6月25日

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  • Ruby Osei-Bonsu,
  • Cecile Sillard,
  • Julien Bras,
  • E. Johan Foster

摘要

Due to their sustainable, versatile, and highly customizable properties, cellulose nanocrystals (CNCs) are regarded as highly promising alternatives to fossil-based materials. However, conventional production of these materials has attracted a lot of environmental and economic concerns, negatively impacting their usability. Subcritical water technology has provided a “greener” yet economic approach to produce these materials with competitive properties. Still, due to the low accessibility of cellulose to water and inhibited esterification reaction rates in the presence of water, the process suffers from low yields of unfunctionalized CNCs. This work employs common mechanical pretreatments (blade grinding, wet ball milling, and refining) to access their fibrillation efficiencies and influence on CNC yield from subcritical water treatment. The initial fibrillation from mechanical pretreatments before subcritical water extraction led to increased exposure and swelling of individual fibers, enhancing maximum solvent accessibility and efficient dissolution of undesirable amorphous regions to increase the overall yield (about 40%) of isolated nanocrystals. During extraction of these materials, the extraction water is catalyzed with an acid blend containing citric acid to produce low surface charge carboxylated CNCs (about 80–200 mmol/kg cellulose). Dispersibility results reveal that the CNCs are colloidally stable in water and maintain this stability for at least 7 days without any sonication. Thermogravimetric analyses also show that these small amounts of surface groups do not negatively affect the thermal stability of the isolated CNCs, having higher thermal stability than sulfated CNCs. The results from this study contribute significantly to improving subcritical water technology for the industrial isolation of high-yield cellulose nanocrystals without using harsh and toxic chemicals.

Graphical abstract